1. Field of the Invention
This invention generally relates to the field of holographic displays. More specifically, this invention relates to producing displays that include three dimensional holographic images and two-dimensional static and/or dynamic images.
2. Description of the Related Art
There is interest is holographic three-dimensional displays that include two-dimensional static and/or dynamic imagery for a variety of applications, including advertising, entertainment, and visualization.
A number of static three-dimensional displays are currently capable of being produced that provide limited animation by angularly multiplexing or linking each frame of animation to a specific horizontal or vertical viewing, angle. As the viewer chances viewing angles with respect to the display, the animation is "played," resulting in perceived motion. These displays, while termed "animated," cannot be updated in real time, and can only contain a few hundred static frames of animation at any time. Updating, the animation involves the time-consuming and costly process of completely re-recording the component images. Thus, these displays are classified as "static" rather than "active" displays.
Currently, there exist real-time imaging systems that can render and display computer generated holograms at video rates. Examples of such systems include holographic video (e.g., the systems described in U.S. Pat. No. 5,172,251 entitled "Three Dimensional Display System," naming Stephen A Benton and Joel S. Kollin as inventors) or LCD-lenticular systems. The displays produced by these systems are classified as active displays. The systems are capable of rendering full color images with up to a 36 degree view zone that range in size from 25.times.25.times.25 to 150.times.75.times.150 millimeters at rates ranging from around 1 to 20 frames per second, depending on the size and view zone of the image. These systems are currently expensive and impractical as they incorporate many complicated moving parts and require extremely high data processing bandwidth to generate and display the images.
Mirrored devices for creating aerial images have been known in the art for many years. Typically, a concave mirror in one form or another is utilized to project an image of an object into space so that to an observer, it appears that a copy of the object is located in a nearby area of space. The copy of the object appears to be levitating in mid-air. While the prior art provides numerous such devices for projecting three-dimensional optical images, the images are in general not "faithful" over a broad range of viewing angles, i.e. not congruent or geometrically similar to the object and must be viewed from a precise angle in order to avoid extreme distortion. Additionally, the prior art devices are not capable of producing images which appear to be located in an area of space far from the mirrored device.
U.S. Pat. No. 5,311,357 discloses a device which positions concave mirrors in a unique arrangement with respect to one another so to produce an image with greater clarity. Additionally, a videotape option allows a whole image to be broadcast and real objects merged with the broadcast image so that the entire combined image appears three-dimensional to a properly located observer. These displays can be classified as combination "active/static" because they incorporate a non-updateable three dimensional subject with a dynamic two dimensional screen display of standard video or film strip imagery.
These mirrored display devices tend to be expensive since there is a direct relationship between the object size and the optical components are that are required to produce the image of the object. Another concern arises in situations where a customer must pay for floor space. Additionally, these displays are not practically scalable, since some of the optics involved must be on the order of twice the size of the images. For example, image sizes over one cubic foot are not practical because they require display systems that are impractically large and cumbersome.
Therefore, with the limited systems of the prior art, projected images are not readily scalable. There exists a need for an improved image projecting device which will provide a large, scalable, faithful three-dimensional image which can be used in numerous applications such as advertising, entertainment, and visualization. It is also important for the improved image projecting device to maintain an occlusion depth cue when the three dimensional image is viewed from various perspectives.